In a saucepan over the stove or in a microwave-safe bowl in the microwave, heat the milk, brown sugar, butter, salt and cinnamon until it gently boils. Add the oats, apple, raisins and walnuts. Transfer the entire mixture to a buttered oven-safe casserole dish, and bake uncovered in the oven for approximately 30 minutes, until not soupy any more but not dried out, either.

Serve each serving as is, or with a few ounces of milk if you prefer. Raw sugar lightly sprinkled on top is optional.